The present invention relates to an improvement in the process for the production of a polymerizate of vinyl chloride, vinylidene chloride or a monomer mixture mainly composed thereof in an aqueous medium in a polymerization reactor, by which the reactor can be opened to the ambient atmosphere without the emission of any unreacted residual monomer or monomers into the atmosphere, so that the residual monomers are completely recovered for re-use.
The polymerization of vinyl chloride, vinylidene chloride or a mixture thereof in an aqueous medium has generally been conducted, using a polymerization reactor containing the aqueous medium and closed hermetically or gas-tight. In the continuous repetition of polymerization runs, the inside of the reactor is required to be inspected from time to time.
When the inspection is carried out, it is a customary practice according to the inventors' plant that after the polymerization is over, the aqueous dispersion of the polymerizate is taken out of the reactor; then fresh air, preceded by nitrogen gas, is introduced to replace the gaseous monomer remaining in the same reactor, the gaseous monomer being emitted into the atmospheric environment; and thereupon the inspector or inspectors enter the reactor. Such a procedure is undesirable from the standpoint of atmospheric pollution because of the emission into the atmosphere of considerably large volumes of the unreacted gaseous monomer or monomers. Moreover, the procedure is disadvantaged by the fact that the replacement of the gaseous monomer by fresh air can not be complete enough, even with prolonged introduction of fresh air, to protect the inspectors entering the reactor from the toxicity of the unreacted gaseous monomer though in a very low concentration.